This invention relates to an electronically-controlled fuel injection system for internal combustion engines, and more particularly to a system of this kind which is intended to improve the driveability of the engine when the engine is in a transient state such as acceleration.
Conventionally, there have been proposed various methods of electronically controlling fuel injection into internal combustion engines in transient states, e.g. by Japanese Provisional Patent Publication (Kokai) No. 60-3458 which is adapted to increase the amount of fuel injected into the engine when the engine is in an accelerating condition, in order to improve the accelerability.
According to the method proposed by Publication No. 60-3458, an accelerating condition of the engine is detected from a rate of change in the opening degree of a throttle valve, i.e. from a rate of depression of the accelerator pedal, and the amount of fuel supplied to the engine is increased based on the detected accelerating condition.
However, the proposed method has the disadvantage that there is a possibility of occurrence of a sudden change in the engine output torque when the engine is in a particular operating condition, which results in vibration of the vehicle body and hence degraded accelerability of the engine.
Specifically, according to the proposed method, an accelerating fuel increment is set to a value appropriate to an engine condition in which the clutch is in an engaged state, i.e., the engine is connected to the transmission. However, when gear shifting is carried out during acceleration of the engine by first disengaging the clutch while closing the throttle valve, shifting gears, and then engaging the clutch while opening the throttle valve, the amount of fuel supplied to the engine is increased based on the change rate in the throttle valve opening degree i.e. the rate of depression of the accelerator pedal. As a result, the engine output torque is excessively increased upon engagement of the clutch, thereby resulting in vibration of the vehicle body and hence degraded accelerability.